KEY WATER HEATING CHARTS AND FORMULAS
by Rich Grimes
It’s 2012 already and in this issue we will try to give you plenty of information and useful charts related to water heating. I don’t receive many requests so I am glad to accommodate on such a pertinent subject. The best part is that you won’t have to read too much from me as these charts and formulas speak for themselves! So here we go…
BTU
A British Thermal Unit (BTU) is a measurement of heat energy. One BTU is the amount of heat energy required to raise one pound of water by 1ºF. Water weighs 8.33 pounds per gallon so we can calculate that one gallon of water requires 8.33 BTU to raise the temperature 1ºF.
BTU CONTENT OF FUELS
ENERGY SOURCE BTU PER HOUR
COAL
1 Pound = 10,000 – 15,000
1 Ton = 25 Million (app.)
ELECTRICITY
1 KW = 3,412
OIL
1 Gallon #1 Fuel = 136,000
1 Gallon #2 Fuel = 138,500
1 Gallon #3 Fuel = 141,000
1 Gallon #5 Fuel = 148,500
1 Gallon #6 Fuel = 152,000
GAS
1 Pound of Butane = 21,300
1 Gallon of Butane = 102,800
1 Cubic Ft. of Butane = 3,280
1 Cubic Ft. of Manufactured Gas = 530
1 Cubic Ft. of Mixed = 850
1 Cubic Ft. of Natural = 1,075
1 Cubic Ft. of Propane = 2,570
1 Pound of Propane = 21,800
1 Gallon of Propane = 91,000
HORSEPOWER
1 Boiler Horsepower (BHP) = 33,475 BTU
1 Boiler Horsepower (BHP) = 34.5 Pounds of Steam @ 212ºF
1 Boiler Horsepower (BHP) = 9.81 KW
COOLING
1 Ton of Cooling = 12,000
GAS INFORMATION
NATURAL PROPANE
Specific Gravity = 0.62 1.52
Flammability Limits (GAS/AIR Mixture) = 4%-14% 2.4%-9.6%
Maximum Flame Propagation (GAS/AIR Mixture) = 10% 5%
Ignition Temperature = 1200ºF 950ºF
1 Pound of Gas (1 PSI) = 28″ Water Column (w.c.)
1 Pound of Gas (1 PSI) = 16 Ounces (oz.)
1 Therm = 100,000 BTU
ELECTRICAL INFORMATION
1 Kilowatt (kW) = 3412 BTU Per Hour
1 Kilowatt (kW) = 1000 Watts Per Hour
1 Kilowatt Hour (kWH) will evaporate 3.5 pounds of water from and at 212ºF
Amperage – Single Phase (1 Ø) = KW x 1000 or WATTAGE
VOLTAGE VOLTAGE
Amperage – Three Phase (3 Ø) = KW x 1000 or WATTAGE
VOLTAGE x 1.732 VOLTAGE x 1.732
WATER HEATING FORMULAS
BTU Per Hour Requirement
BTU OUTPUT = GPM x Temperature Rise x 8.33 Lbs/Gallon x 60 Minutes
BTU INPUT = (GPM x Temperature Rise x 8.33 Lbs/Gallon x 60 Minutes)
% Efficiency
Heat Transfer Efficiency
% EFFICIENCY = (GPH x Temperature Rise x 8.33 Lbs/Gallon)
BTU/Hr INPUT
Heat-Up Time
Time in Hours = (GPH x Temperature Rise x 8.33 Lbs/Gallon)
(BTU/Hr INPUT x % Efficiency)
Temperature Rise
Temp. Rise (∆T) = (BTU/Hr INPUT x % Efficiency)
(GPM x 60 Minutes x 8.33 Lbs/Gallon)
GPH Recovery
Electric = (kW INPUT x 3412 BTU/kW x % Efficiency)
(Temperature Rise x 8.33 Lbs/Gallon)
Gas = (BTU/Hr INPUT x % Efficiency)
(Temperature Rise x 8.33 Lbs/Gallon)
MIXED WATER FORMULA
% of Hot Water Required = (Mixed Water ºF – Cold Water ºF)
(Hot Water ºF – Cold Water ºF)
WATER INFORMATION
1 Gallon = 8.33 Pounds
1 Gallon = 231 Cubic Inches
1 Cubic Ft = 7.48 Gallons
1 Cubic Ft = 62.428 Pounds (at 39.2ºF – maximum density)
1 Cubic Ft = 59.83 Pounds (at 212ºF – boiling point)
1 Ft of Water Column (w.c.) = .4333 PSI
Water expands 4.34% when heated from 40ºF to 212ºF
Water expands 8% when frozen solid
OPEN VESSEL
BOILING POINT @ 0 PSI ALTITUDE
212ºF 0 Feet (Sea Level)
210ºF 1000 Feet
208ºF 2000 Feet
207ºF 3000 Feet
205ºF 4000 Feet
203ºF 5000 Feet
201ºF 6000 Feet
199ºF 7000 Feet
CLOSED VESSEL BOILING POINT @ PSI @ Sea Level
BOILING POINT GAUGE PRESSURE
212ºF 0 PSI
240ºF 10 PSI
259ºF 20 PSI
274ºF 30 PSI
287ºF 40 PSI
298ºF 50 PSI
316ºF 70 PSI
331ºF 90 PSI
ONLINE RESOURCES
There are an unlimited number of online tools and calculators for every mathematical formula. The internet is full of helpful resources to get the job done quicker. Here are a few links to some useful websites:
WEBSITE/PROGRAM WEB ADDRESS
Amtrol Expansion Tank Sizing http://amtrol.com/support/sizing.html
Engineering Toolbox Calculators http://www.engineeringtoolbox.com/
State Water Heater Sizing (Online) http://www.statewaterheatersizing.com/
AO Smith Water Heater Sizing (Online) http://www.hotwatersizing.com/
Lochinvar Water Heater Sizing (Download) http://www.lochinvar.com/sizingguide.aspx
Cylinder Calculator (Storage Tanks) / Other Math Calculators http://www.calculatorfreeonline.com/calculators/geometry-solids/cylinder.php
Electrical/Mechanical/Industrial/Civil/Chemical/Aeronautical Calculators http://www.ifigure.com/engineer/electric/electric.htm
B&G System Syzer (Piping/Pressure Drop Tool Download) http://completewatersystems.com/brand/bell-gossett/selection-sizing-tools/system-syzer/
B&G Selection and Sizing Tools (Pumps, Regulators, Steam and Condensate) http://completewatersystems.com/brand/bell-gossett/selection-sizing-tools/
Taco Pump Selection Wizard (Online Pump Selector) http://www.taco-hvac.com/en/wizard_pumps.html
Lawler Mixing Valve Sizing (Online – account setup) http://www.lawlervalve.com/index.php?p=page&page_id=Sizing_Program
DSIRE Database of State/Federal Renewable Energy Rebates http://www.dsireusa.org/
ASCO Valve Online Product Selector (Valves – solenoid, pilot, pneumatic, etc.) http://www.ascovalve.com/Applications/ProductSearch/ProductSearch.aspx?ascowiz=yes
SUMMARY
There is a lot of other information that we could add such as Steam. It is a viable heating source and there are several factors that must be considered such as operating pressure, steam trap and condensate line sizing and so on. We will have to do a separate article on Steam in a future issue.
The charts and information above are all essential to water heating. They are proven mathematical formulas of algebra and geometry. If you input the accurate information then the results will be correct. It is also good to use the online tools and calculators. They are true time savers.
Thanks and we’ll see you in the next article!
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